This invention relates in general to rotary solenoids and more specifically to rotary solenoids utilizing permanent magnets for generating shaft torque and rotational movement.
Prior art rotary actuators of one type are exemplified by the patent to Leland et al., U.S. Pat. No. 3,264,530. Leland '530 discloses a rotary actuator adapted to convert an axial thrust to rotary movement. Magnetic forces developed axially are converted into rotary motion by inclined ball bearing races in the Leland device. A similar concept is employed in the rotary latching solenoid shown in Burton, U.S. Pat. No. 4,660,010. Axial forces imported to ball bearings in the Burton device facilitate rotary movement of the armature. Magnetic forces developed by way of current flowing through a coil latch the Burton device into the rotated position.
Still further examples of rotary solenoid devices are shown in U.S. Pat. No. 4,157,521 to Leland, and U.S. Pat. No. 3,278,875 to McDonough. The device disclosed in the '521 patent includes a multilobe armature attracted to magnetized pole pieces, thereby inducing rotary motion. The magnetic forces are created by current flowing through a coil. Ball bearing races limit the rotary travel of the '521 device. The novel concept in the '521 patent is a constant air gap wherein the shaft is not displaced axially during rotary movement of the actuator. McDonough discloses a similar rotary actuator concept wherein permeable metal is attracted to magnetized pole pieces thereby creating rotary motion.
A further example of coil induced magnetic fields causing or inducing rotary motion by way of magnetic forces is shown in Vogel, U.S. Pat. No. 4,275,371. Vogel discloses an armature shaft having magnets attached to the lateral surface of the shaft. Rotary motion is induced by way of magnetic forces created at three different points around the armature by electromagnets. A further example of a rotary solenoid using electromagnets and permanent magnets to induce rotary motion is the patent to McClintock, U.S. Pat. No. 4,135,138. McClintock discloses a device incorporating electromagnets to generate attracting and repelling forces for inducing rotary motion.
Further examples of solenoid actuators and/or linear actuators are shown in Ueno et al., U.S. Pat. No. 3,838,370, which discloses a linear actuating device. In addition, Belgian Pat. No. 648446 to Kommandit, and Russian Pat. No. SU 769-654 to Tyutkin disclose magnetically activated devices which produce axial or rotary motion.
A primary disadvantage of prior art devices which transform axial forces into rotary forces is that the force angles involved are so great and the force component so small that there is a great loss of force and torque in the transformation of the axial to the rotary motion. Further, devices such as that shown in McDonough, which attempt to overcome the shortcomings of the axial thrust devices include return springs which directly reduce the amount of torque developed by the magnetic circuitry components of the rotary actuator.
McClintock attempts to overcome the limitation imposed by the return spring forces as no return spring is included in the rotary solenoid device disclosed therein. Additionally, it should be noted that the space necessary to accommodate the requisite return spring in some of the prior art devices is eliminated by the McClintock design. The device disclosed in McClintock relies upon attractive forces developed between magnets mounted on a rotor and the surrounding housing to develop a magnetic force inducing rotary motion.
An electrical rotary actuator or solenoid which eliminates return springs, provides high torque response, and eliminates expensive bearing assemblies utilized in prior art devices to transform linear motion into rotary motion is disclosed herein.